Providing a new method for protecting the loss of excitation of generator in the presence of phase‐shifting transformer

Abstract

Summary The use of phase shifting transformer (PST) is one of the common methods of power flow control in complex transmission systems. Changing the power distribution in lines by the PST will change the voltage and the current signals of the power system. Loss of excitation relay in a synchronous generator is one of the important relays of the generator that measures the voltage and current signals of generator output to identify the loss of excitation of the generator. This study shows that the presence of PST in the transmission line interferes with the performance of the loss of excitation (LOE) relay. The LOE relay in this paper is of the Berdy type, which detects loss of excitation by measuring the voltage and current of the generator and calculating the impedance from them. In this paper, the way this impedance is calculated has been modified, as this impedance is calculated from the modified values of the active and reactive powers of the generator. As a result, it has been shown that with the help of this method, the effect of PST on the operation of the LOE relay is significantly eliminated. In the proposed method, PST information is not required to be sent to the relay location, and so the communication channel is not needed. A decision tree‐based method is used as a backup protection to guarantee proper operation in power swing conditions.